Renal drug excretion

ALAN TALEVI; CAROLINA L. BELLERA

The ADME Encyclopedia. A Comprehensive Guide on Biopharmacy and Pharmacokinetics

Springer Nature

Lugar: Basignstoke; Año: 2022; p. 1059 - 1065

Together with the liver, the kidneys are one of the major organs involved in drug elimination, having the ability to both excrete and metabolize drugs. Glomerular filtration, active tubular secretion and tubular reabsorption are the fundamental processes determining the rate of urinary excretion of a drug. The functional unit of the kidney is the nephron (Figure 1), which first filters the plasma from the blood and then converts it to urine. Filtration takes places at the glomerular capillaries enclosed in the Bowman?s capsule. The filtrate subsequently flows into the proximal tubule, where about 80-90% of the filtered water is reabsorbed and active systems secrete organic cationic and anionic drugs. Both phenomena contribute to the creation of a concentration gradient between the tubular content and peritubular capillary blood, leading to reabsorption of substances in the tubular lumen. Passive diffusion across the tubular membrane is the primary mechanism of reabsorption for most drugs, while carrier-mediated reabsorption is associated with physiological compounds, such as vitamins or amino acids, as well as drugs resembling such substances [1, 2].